Lead glass composition



Patented Nov. 13, 1945 7 UETED STATES A 2,388,866 PATENT orrice 2,388,866 LEAD GLASS comosrriou John H. Partridge, Pinner, England, assignor to General Electric Company, a corporation oi.

New York No Drawing. Application January 29, 1944, Se-

1'i9ag2No. 520,325. In Great Britain November 5,

3 Claims.

. of lead oxide.

I have now found that the presence of strontium oxide makes itpossible to reduce the.

working range is 04-0-1. mo Km are respectively the resistivities in ohm cm. at 150 C. and 200 C. The column headed I refers to a known glass or the type specified; the columns headed II and III refer to the two glasses according to the invention. j

It will be noted that theresistivity of these three glasses is somewhat higher than that or many of the lead glasses that are widely used.

The lower proportion of lead makes them also less liable to scum during founding, and suitable for founding in a tank.

What I claim as new and desire to secure by Letters Patent oi the United States is:

1. I lead glass having approximately the following composition:

content of lead oxide. According to the inven- Per cent tion, therefore, a glass of the type specified con- S102 583 tains at least 2 per cent of strontium oxide and: 1919 not more than 20 per cent or lead oxide. A1203 5 It does not appear possible to replace the lead Bao- 238 oxide removed wholly by strontium oxide; the Bro 252 substituents for lead preferably include some or M80 133 all of the oxides of barium, magnesium, boron. B30: 190 and titanium as well as strontium oxide. The Q N830 53 strontium oxide also makes it possible to reduce mo 73 the content of potassium oxide. However, again a it does not appear possible by the introduction 2-. A lead 81 l! ap im tely the I of strontium oxide both to reduce the potassium lowing comwfllflom oxide content to not more than 3 per cent, and a Perm; to reduce the lead oxide content to not more than per cent. 810: I I Two glasses according to the invention will now PbO 7 9.8 be described by way of example with reference to AiaOi 3 the following table. The upper rows give the ,BaO 358 composition of the glasses. In the lower rows, ,SrO' a is the coeflicient of linear expansive per C. M50 43 over the range 20 to 350 C., 03, 04,. 01, are re- NaaO 1 spectlvely the temperatures in C.-at which the K20 5.86 viscosity of the glass 1510, 10 10 poise. The as T102- airworthi ss-mud. characterised by case otworking combined wlthhilh electricnl resistivity, containing the usual compo-- -nentlot theleadg loncsmedinelechiclamps,- lncludinlflioalethemaiorcomponentandmbproportions oLPbO metal.

oxidegandcharacterinedbythepnsenceotthd oxidesotflnneandllmthesiobeinapreeent in an'nmount ot-at least 2%, together within amoimtotrbolecatlianlifi.

I roman. ammer. 

